The field of the invention is cleaning apparatus for cleaning carriers used to hold and transport semiconductor wafers and similar flat articles requiring low contamination levels.
The processing of semiconductor wafers, substrates, photomasks, flat panel displays, data disks, optical and MEMS media and other flat articles (collectively referred to here as xe2x80x9cwafersxe2x80x9d) is very sensitive to contamination. These articles require extremely low contamination levels. Even microscopic contaminants can cause defects. Accordingly, it is necessary to maintain a high level of cleanliness during virtually all stages of manufacture.
Wafers are typically processed in batches. Batch handling may occur throughout the entire production process, or for one or more processing steps or related handling operations. Batch processing usually uses a carrier to hold the wafers. The wafer carriers can be of various designs and are generally a protective case or box optionally including a removable door. These carriers or boxes are known as FOUPs, FOSBYs or cassettes. In these types of carriers, the wafers are held and enclosed, to protect them from contamination during movement and storage within the processing facility. After each use, the wafer carriers must generally be cleaned to avoid having particles and contaminants on the carriers contaminate the wafers. Cleaning the boxes, however, can be difficult because they typically have features such as slots, grooves, and/or apertures.
Carriers have been successfully cleaned in centrifugal cleaners. See, for example, U.S. Pat. No. 5,738,128 incorporated herein by reference. In these centrifugal cleaners, the box is loaded onto a rotor, with the open front side of the box facing radially outwardly from the rotor. The box is then sprayed with cleaning fluids, and then with drying gases, while the rotor turns. Centrifugal force helps to remove cleaning fluids from the box, to help dry it. While these techniques have worked well for different types of boxes, disadvantages remain in loading, holding and unloading especially larger size carriers.
Another engineering challenge is that carrier doors in current systems are generally cleaned separately from the boxes themselves. Accordingly, matching the doors back with their respective boxes after cleaning is often difficult, error prone, and time consuming. Thus, there is a need for a system that efficiently cleans carriers, as well as a system that cleans carriers and carrier doors together.
In a first aspect of the invention, a system for cleaning carriers used for holding flat media or wafers includes a rotor rotatably mounted within an enclosure. Spray nozzles in the enclosure spray fluid toward the rotor. The rotor has at least one box holder assembly for holding a box, such as a FOUP or FOSBY. At least one retainer bar is located on the rotor for engaging a front section of the box to retain the box in the box holder assembly during rotation of the rotor. In a preferred embodiment, the retainer bar is moveable from a first position where the retainer bar restrains the box on the box holder assembly, to a second position where the retainer bar is moved away from the box. This design provides for quick, reliable and ergonomic loading, securing and unloading of boxes.
In a second aspect of the invention, the box holder assembly includes a base for supporting a box. The base includes a plurality of grooved elements that are adapted to engage a flange on the box for securing the box to the box holder assembly.
In a third aspect of the invention, a method of cleaning a box used for handling flat media includes loading a box into a box holder assembly on a rotor preferably via handles on the box. A retainer bar is then moved into engagement with the box to secure the box into the box holder assembly before rotating and spraying the box. The boxes are securely held in the rotor.
In a fourth aspect of the invention, a method of cleaning a carrier having a box with a removable door includes separating the door from the box and loading the box into a box holder assembly on a rotor. The door is then loaded into a door holder assembly attached to and alongside of the box holder assembly. Since each door remains next to its box at all times, matching doors and boxes after cleaning is greatly simplified.
In a fifth aspect of the invention, a rotor for holding and rotating boxes during cleaning of the boxes includes a top plate and a base plate. A plurality of columns of box holder assemblies or ladders are attached between the top plate and the bottom plate. The box holder assemblies in each column have open front ends which are oriented perpendicularly to the box holder assemblies of the neighboring or adjacent columns. This provides for a more compact apparatus.
In a sixth aspect of the invention, a rotor for holding and rotating boxes during cleaning of the boxes includes a top plate and a base plate. A plurality of box holder assemblies are located between the top plate and the bottom plate. Each box holder assembly includes a base plate or other means for holding a box, and a door plate or other means for holding a door, with the door plate attached to the base plate. Each box door is cleaned while remaining adjacent to the box the door came from.
Other and further objects, inventive features, and advantages, will appear hereinafter. The invention resides as well in subsystems and subcombinations of the features described. While various additional elements are discussed in the following detailed description, these elements are not essential to the invention.